JP5259296B2 - Planar illumination device and liquid crystal display device using the same - Google Patents

Description

  The present invention relates to a planar illumination device using laser light as a light source, and a liquid crystal display device using the same, and more specifically, a thin planar illumination device with high light utilization efficiency that can be applied to a large screen, and The present invention relates to a liquid crystal display device using the same.

  In a liquid crystal display device used for a display panel or the like, a planar illumination device in which a light source such as a discharge tube or a light emitting diode (LED) is generally used as backlight illumination. When these planar illumination devices are used for large displays or the like, light with high luminance and strong monochromaticity is required, and in recent years, a configuration using a laser light source has been started.

  Such a display panel is required to be devised to make the luminance uniform by eliminating luminance unevenness on the entire display panel surface, or to devise to improve power utilization efficiency and reduce power consumption. In recent years, with the increase in size, there is an increasing demand for thinning for applications such as wall-mounted TVs.

  As a method for thinning a planar lighting device used for a display panel, there is an edge light method. In the edge light method, light is incident from the side surface of the light guide plate, incident light is deflected toward the main surface by a deflection groove or a scatterer provided on the back surface of the light guide plate, and light is emitted from the main surface of the light guide plate. This is a method for obtaining planar illumination. The edge light system has a feature that it can be made thinner than a so-called direct type system in which light sources are arranged in a plane.

  In this edge light system, as a configuration for realizing a large screen and high luminance, a configuration in which light is incident from both side surfaces of the light guide plate has been proposed. For example, in the configuration described in Patent Document 1, the light guide plate has a flat surface (main surface) on the liquid crystal display panel side, and a surface (back surface) on which a deflection groove opposite to the main surface is formed is light. Is formed so that the wall thickness becomes thinner as it goes from the both side surfaces to which light is incident toward the center (that is, in an inverted V shape). With such a configuration, the light guide plate is also reduced in weight.

  In addition, in order to cope with an increase in screen size, it is also required to increase the output of the light source. This can be dealt with by using a high-power laser light source. As a configuration using a laser light source, for example, the configuration proposed in Patent Document 2 can be used. Patent Document 2 proposes a configuration in which LEDs are arranged on both sides of a rod-shaped light guide. However, if the LEDs are replaced with a high-power laser light source in this configuration, a high-power linear light source can be realized. Can be applied to large screen displays.

In order to realize a thin and large-screen display, it is considered suitable to combine a high-power laser light source with the light guide plate structure proposed in Patent Document 1. Moreover, the structure proposed in Patent Document 2 can be used to linearize the light from the laser light source.
JP 2001-228477 A Japanese Patent Laid-Open No. 11-271767

  However, even in a structure in which Patent Document 1 and Patent Document 2 are combined, part of the light incident from the side surfaces on both sides of the light guide plate reaches the side surface opposite to the incident side, and from there. There has been a problem that light is emitted to reduce the light utilization efficiency. Hereinafter, this problem will be described.

  FIG. 12 is a diagram illustrating a schematic configuration of a conventional planar illumination device 100 having a structure in which Patent Document 1 and Patent Document 2 are combined. In particular, FIG. 12A shows a schematic configuration diagram of the planar illumination device 100 as viewed from above. FIG. 12B shows a schematic diagram of the configuration of the side surface of the main part of the planar illumination device 100 as seen from the direction of the arrow E in FIG.

  12A and 12B, the planar illumination device 100 includes laser light sources 101 to 104, rod-shaped light guides 105 and 106, and a light guide plate 107. The light guide plate 107 is configured such that the main surface 107a from which light is emitted is a flat surface, and the back surface 107b becomes thinner toward the center. A deflection groove that deflects light incident on the light guide plate 107 toward the main surface 107a is formed on the back surface 107b.

  In the planar illumination device 100 configured as described above, the laser light emitted from the laser light sources 101, 102, 103, 104 is converted into a linear light source by the light guides 105, 106 and enters the light guide plate 107. . For simplicity, in FIG. 12B, only the laser light emitted from the light guide 106 is indicated by a dotted line, and the laser light emitted from the light guide 105 is omitted. As shown in FIG. 12B, a part of the light beam 108 of the light incident on the light guide plate 107 passes through the light guide plate 107 and reaches the opposite side surface, causing a light amount loss.

  Therefore, an object of the present invention is to solve the above-described conventional problems, and to provide a planar lighting device that is thin and has high light utilization efficiency applicable to a large screen, and a liquid crystal display device using the same. is there.

  In order to achieve the above object, a planar illumination device according to the present invention includes a linear light source unit that emits a linear laser beam, and linear laser beams that are incident from both end surfaces facing each other. A light guide plate that exits from the light source. The main surface of the light guide plate is composed of a plurality of inclined surfaces, and the light guide plate is configured such that the thickness decreases toward the center.

  At this time, the thickness of the central portion of the light guide plate is preferably thinner than the thickness of the end faces on both sides of the light guide plate.

  As a result, the surface illumination device can obtain high uniformity in the light emitted from the light guide plate, and can reduce the light incident from the end surface of the light guide plate from being emitted from the opposite end surface. Efficiency can be increased.

  Preferably, the light guide plate has a deflecting body that deflects light incident on the light guide plate toward the main surface on the back surface facing the main surface, and at least one of the plurality of inclined surfaces virtually defines the inclined surface. When extended, it is configured to intersect with part of the back surface. Thereby, it can prevent that the light which injected into the light-guide plate radiate | emits from the end surface on the opposite side.

  At this time, the main surface of the light guide plate is preferably composed of two inclined surfaces that are inclined from the end surfaces on both sides toward the center, and the light guide is preferably configured such that the main surface side is concave. Thereby, the uniformity of the light emitted from the light guide plate can be improved and the light can be prevented from leaking from the end face of the light guide plate.

  Alternatively, the main surface of the light guide plate is composed of two inclined surfaces that are inclined from the end surfaces on both sides toward the center, and one flat surface that connects between the two inclined surfaces. It is desirable to be configured as follows.

  The planar illumination device further includes a prism sheet that adjusts an emission angle distribution of light emitted from the light guide plate, and the prism sheet is disposed along the inclined surface of the light guide plate. Thereby, the loss in recycling of light can be reduced and the light utilization efficiency can be further increased.

  The planar illumination device may have a configuration in which a diffusion plate or a lenticular lens is disposed on the main surface side of the light guide plate. Since the distance between the bottom surface of the light guide plate and the diffusion plate or lenticular lens can be increased depending on the shape of the light guide plate, the emitted light can be made uniform even if the light guide plate is thin.

  A fine periodic structure may be formed on the inclined surface of the light guide plate. Thereby, the effects of deflection separation and wavelength separation can be obtained.

  Preferably, a space between the inclined surface of the light guide plate and the diffusion plate or the lenticular lens is sealed. Thereby, the fine periodic structure formed in the inclined surface of the light guide plate can be protected.

  Or the main surface of a light-guide plate is comprised from four inclined surfaces arrange | positioned in series between the end surfaces of both sides, and the light guide plate has a convex V-shape with two central inclined surfaces among the four inclined surfaces. It is desirable to have a shape. Thereby, since the distance which light propagates the inside of a light-guide plate can be shortened, the absorption loss of the light in a light-guide plate can be reduced.

  The main surface of the light guide plate is composed of a plurality of inclined surfaces configured to be thinner toward the center, and a plurality of incident surfaces arranged between the inclined surfaces. The plurality of incident surfaces are configured such that substantially parallel light irradiated from both end face directions is incident thereon. Accordingly, the light guide plate can be reduced in weight, and the light absorption loss in the light guide plate can be reduced.

  The light guide plate may contain minute diffusion particles inside. Accordingly, it is possible to further reduce the light amount loss due to light emitted from the side surface opposite to the incident surface through the inside of the light guide plate.

  The linear light source unit is configured to emit light substantially parallel to the main surface of the light guide plate toward the end surfaces on both sides of the light guide plate, and the light guide plate is arranged on the back surface facing the main surface. A large number of deflecting grooves for deflecting substantially parallel light incident from the surface by total reflection are formed. Thereby, most of the light incident on the light guide plate is deflected by total reflection and emitted from the main surface, so that the light use efficiency can be improved.

  The linear light source unit emits substantially parallel light in a direction orthogonal to the thickness direction of the light guide plate, and is polarized horizontally or vertically with respect to the inclined surfaces adjacent to the end surfaces on both sides of the light guide plate. The light guide plate is configured to emit light that is substantially parallel to the end surfaces on both sides. Further, the deflection groove is configured to be parallel to the end surfaces on both sides.

  Thereby, since light with uniform polarization is emitted from the light guide plate, the transmittance of the liquid crystal display panel is improved when combined with the liquid crystal display panel, and the light utilization efficiency is improved.

  The linear light source unit includes a laser light source that emits divergent light, a collimator element that converts the divergent light emitted from the laser light source into substantially parallel light, and the light emitted from the collimator element is incident from the end surface and is emitted from the side surface. A configuration including a rod-shaped light guide is desirable.

  Alternatively, the linear light source unit includes a laser light source that emits divergent light, a collimator element that converts the divergent light emitted from the laser light source into substantially parallel light, and a polygon mirror that deflects and scans the light emitted from the collimator element. A configuration including this is desirable.

  Alternatively, the linear light source unit includes a laser light source that emits divergent light, a collimator element that converts the divergent light emitted from the laser light source into substantially parallel light, and the light emitted from the collimator element by primary refraction, diffraction, or scattering. A configuration including a one-dimensional diffusion element that diffuses in the original direction is desirable.

  With these configurations, a linear light source unit that emits substantially parallel light can be realized.

  At this time, it is desirable that the light guide plate is configured such that the deflection groove is a curved surface, and the tangent of the curved surface is 30 ° to 60 ° with respect to the main surface. Thereby, since the viewing angle of the light emitted from the light guide plate can be adjusted and emitted, the number of viewing angle adjustment sheets can be reduced, and the cost can be reduced.

  Preferably, the light guide plate is formed by injection molding, and the gate is provided at the thinnest portion of the side surface orthogonal to the light incident surface. Thereby, at the time of light-guide plate manufacture, resin can be made to flow easily, a residual stress can be reduced, and birefringence can be reduced.

  The linear light source unit is disposed on the longitudinal side surface of the light guide plate. Thereby, the distance which light propagates in the inside of a light-guide plate can be shortened, and the light absorption loss in a light-guide plate can be reduced.

  Further, the planar illumination device of the present invention includes a laser light source that emits laser light, a rod-shaped light guide that is made to enter the laser light from opposite end surfaces and that is emitted from the side surface, and light that is emitted from the light guide. With a light guide plate that enters from the end face and exits from one main face. The light guide is formed so that a cross section parallel to the end faces on both sides is rectangular, and the side surface from which the light of the light guide is emitted is inclined to be thinner toward the center of the light guide. It consists of an inclined surface.

  As a result, high uniformity can be obtained in the light emitted from the light guide, and the light incident from the end face of the light guide can be reduced from being emitted from the end face on the opposite side, thereby improving the light utilization efficiency. Can do.

  The side surface from which the light of the light guide is emitted is composed of two inclined surfaces that are inclined from the end surfaces on both sides toward the center, and the light guide is configured so that the side surface is concave. Thereby, the uniformity of the light emitted from the light guide is improved, and the light can be prevented from leaking from the end face of the light guide.

  Alternatively, the side surface from which the light of the light guide is emitted is composed of two inclined surfaces that are inclined from the end faces on both sides toward the center, and a single plane that connects between the two inclined surfaces. The side surface is configured to be concave.

  Alternatively, the side surface from which the light of the light guide is emitted is composed of four inclined surfaces arranged in series between the end surfaces on both sides, and the light guide has two inclined surfaces in the center among the four inclined surfaces. It is configured to have a convex V shape. Thereby, since the distance which light propagates in the inside of a light guide can be shortened, the absorption loss of the light in a light guide can be reduced.

  In order to achieve the above object, the liquid crystal display device of the present invention includes a liquid crystal display panel and a backlight illumination device that illuminates the liquid crystal display panel from the back side. The backlight illumination device has been described above. Any planar lighting device is used.

  With this configuration, it is possible to realize a liquid crystal display device that has good color reproducibility even on a large screen, high luminance, and little luminance unevenness. A thin liquid crystal display device can also be realized.

  According to the present invention, a thin planar lighting device with high light utilization efficiency using a laser light source can be realized. By using this planar lighting device as a backlight lighting device, the color reproduction range is wide and the area is large. This has a great effect that a thin display device with high luminance can be realized.

  These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the same components are denoted by the same reference numerals, and description thereof may be omitted. Moreover, about drawing, in order to assist an understanding, each component is typically shown mainly, and about a shape etc., it is not an exact display.

(First embodiment)
FIG. 1 is a diagram illustrating an example of a schematic configuration of a planar illumination device 10 according to the first embodiment of the present invention. Fig.1 (a) has shown the schematic block diagram of the planar illuminating device 10 seen from the upper surface. FIG.1 (b) has shown the schematic diagram of the structure of the side surface of the principal part of the planar illuminating device 10 seen from the direction of arrow A of Fig.1 (a). FIG.1 (c) has shown the enlarged view of B part of FIG.1 (b).

  1A and 1B, the planar illumination device 10 includes light source parts 15, 16, 17, 18, light guides 19, 20, and a light guide plate 21. The light source unit 15 includes a laser light source 11 and dichroic mirrors 13 and 14. The laser light source 11 includes a red laser light source (R light source) 11R that emits red laser light (R light) 12R, a green laser light source (G light source) 11G that emits green laser light (G light) 12G, and blue laser light ( It comprises a blue laser light source (B light source) 11B that emits (B light). The dichroic mirrors 13 and 14 multiplex the red laser light (R light) 12R, the green laser light (G light) 12G, and the blue laser light (B light) 12B. The light source units 16, 17, and 18 have the same configuration as the light source unit 15, and thus description thereof is omitted. The light source units 15, 16, 17, and 18 and the light guides 19 and 20 constitute a linear light source unit.

  Here, the R, G, and B light sources 11R, 11G, and 11B built in the light source units 15 to 18 are configured so that the polarization is substantially horizontal or substantially perpendicular to the main surfaces 21a and 21b of the light guide plate 21, respectively. , R light, G light, and B light are all configured to be in the same direction. Although not shown, each of the RGB light sources 11R, 11G, and 11B has a collimator lens and is configured to emit substantially parallel light.

  Laser light is incident on the light guides 19 and 20 from the light source units 15, 16, 17, and 18. The light guides 19 and 20 are configured in such a manner that the four surfaces excluding the surface on which light is incident in a quadrangular prism shape are horizontal or perpendicular to the polarization of the light emitted from the light source units 15 to 18, and the side surface 19b. , 20b is deflected by total reflection and directed toward the exit surfaces 19a, 20a. Further, a deflection groove having an inclined surface of approximately 45 degrees with respect to the emission surfaces 19a and 20a is formed.

  The light guide plate 21 receives light from the side surfaces (incident surfaces) facing the light guides 19 and 20, and emits irradiation light 24 from the main surfaces 21a and 21b. The light guide plate 21 is configured such that the main surfaces 21a and 21b are inclined from the incident surface toward the center, and the main surfaces 21a and 21b extend virtually toward the opposite incident surface, respectively. It is comprised so that the back surface 21c may be crossed.

  Further, as shown in FIG. 1C, a deflection groove is formed on the back surface 21c to deflect the light incident on the light guide plate 21 by total reflection and to direct the light toward the main surfaces 21a and 21b. The deflection groove has a curved surface obtained by continuously connecting, for example, inclined surfaces of 40 to 60 degrees with respect to the main surfaces 21a and 21b. The deflection groove is configured to be substantially parallel to the incident surface.

  Next, operation | movement of the planar illuminating device 10 comprised in this way is demonstrated. In FIG. 1A, laser light 12R, 12G, and 12B emitted from the R light source 11R, the G light source 11G, and the B light source 11B, for example, with polarized light substantially parallel to the main surface 21a of the light guide plate 21, are dichroic mirror 13, 14 is combined into one laser beam as RGB light and emitted from the light source unit 15. Similarly, a laser beam in which RGB light is combined into one with a polarization substantially parallel to the main surface 21a is emitted from the light source unit 16. Further, the light sources 17 and 18 emit laser light in which RGB light is combined into one light with polarization substantially parallel to the main surface 21b. Laser light emitted from the light source units 15, 16, 17, and 18 is converted into a linear light source by the light guides 19 and 20 and is incident on both side surfaces of the light guide plate 21.

  Here, since each side surface of the light guides 19 and 20 is perpendicular to the polarization plane of the light emitted from the light source units 15, 16, 17 and 18, or parallel to the polarization, Polarized light is retained when reflected and propagated inside 20. Therefore, light with uniform polarization is emitted from the light guides 19 and 20 perpendicularly to the emission surfaces 19a and 20a, and is incident at an angle substantially parallel to the main surface 21a or the main surface 21b of the light guide plate 21. To do. At this time, the incident surface of the light guide plate 21 may be configured to be inclined with respect to the incident light, and the incident light may be refracted by the incident surface so as to be incident substantially parallel to the main surface 21a or the main surface 21b.

  The propagating light 22 incident on the light guide plate 21 from the light guide 19 side travels in the light guide plate 21 substantially in parallel with the main surface 21a, and most of the light flux is totally reflected by the deflection groove provided on the back surface 21c. And is emitted as the irradiation light 24 from the main surface 21a or the main surface 21b.

  At this time, since the main surface 21a of the light guide plate 21 is extended so as to intersect with the back surface 21c, the propagation light 22 propagating substantially parallel to the main surface 21a passes through the light guide plate 21 and is on the opposite side. It does not come out from the side surface, and it is possible to prevent light loss that has been a problem in the conventional configuration. The same applies to the propagation light 23.

  At this time, the deflection grooves provided on the back surface 21c are configured to be parallel to the incident surface, that is, perpendicular to the propagating light 22 and 23 inside the light guide plate 21. Light is emitted.

  The planar illumination device 10 configured in this way is configured so that the incident light to the light guide plate 21 is substantially parallel light, and all the propagating light that reaches the deflection groove satisfies the total reflection condition, so that the light is extremely high. Use efficiency is obtained. In addition, even when substantially parallel light is incident on the light guide plate 21, the light is not emitted from the side surface opposite to the incident surface through the light guide plate 21 and the amount of light is not lost as in the conventional configuration.

  Further, the planar illumination device 10 has a curved surface of the deflection groove provided on the back surface 21c of the light guide plate 21 so that the emission angle of the irradiation light 24 is ± 30 degrees with respect to the direction orthogonal to the deflection groove. Therefore, the number of viewing angle adjustment sheets can be reduced in order to adjust the viewing angle in this direction. Thereby, cost reduction can be achieved.

  Further, the planar illumination device 10 can be configured to be thin and has an advantage of emitting light with uniform polarization. Moreover, since light is incident from both side surfaces of the light guide plate 21, light with excellent uniformity can be emitted.

  Furthermore, the planar illumination device 10 can be used as a backlight illumination device for a liquid crystal display device such as a large display or a high brightness display. FIG. 2 is a diagram showing a schematic configuration of a liquid crystal display device 40 using the planar illumination device 10 of FIG. 1 as a backlight illumination device. In the liquid crystal display device 40 shown in FIG. 2, a liquid crystal display panel 30 is added to the planar illumination device 10 shown in FIG. The liquid crystal display device 40 includes the liquid crystal display panel 30 and the planar illumination device 10. The planar illumination device 10 is the same as that shown in FIG.

  In FIG. 2, the liquid crystal display panel 30 includes a polarizing plate 31, a glass plate 32, a liquid crystal 33, RGB pixels 34, a color filter 35, a glass plate 36, and a polarizing plate 37. Here, the direction of the transmission axis of the polarizing plate 31 is configured to coincide with the polarization direction of the irradiation light 24 of the planar illumination device 10.

  In the liquid crystal display device 40 configured as described above, the irradiation light 24 emitted from the planar illumination device 10 transmits most of the light through the polarizing plate 31 of the liquid crystal display panel 30, passes through the glass plate 32, and is liquid crystal. 33 and the RGB pixels 34, pass through the color filter 35, the glass plate 36 and the polarizing plate 37 and are displayed as an image on the liquid crystal display device 40.

  The liquid crystal display device 40 of the present embodiment configured as described above can realize a thin liquid crystal display device with wide color reproducibility by using a laser as a light source. In addition, since the backlight illumination is aligned, there is little loss at the polarizing plate on the backlight side, high brightness and low power consumption can be achieved, and there is no uneven brightness, and high quality liquid crystal display is achieved with uniform backlight illumination. A device can be realized.

  In the planar illumination device 10 of the present embodiment, the R light, G light, and B light emitted from the laser light source 11 are combined by the dichroic mirrors 13 and 14, but each light is separately guided to the light guide. It is good also as a structure which injects into 19 and 20, and combines inside the light guides 19 and 20. FIG.

  In the present embodiment, the rear surface 21c of the light guide plate 21 is provided with a deflection groove so that substantially parallel light is incident and the light is efficiently extracted. However, the rear surface 21c of the light guide plate 21 is a flat surface, and the reflective scatterer is used. It is good also as composition applied by printing etc. Further, the light guide plate 21 may include minute diffusion particles inside. Thereby, it is possible to further reduce the possibility that light passes through the light guide plate 21 and is emitted from the side surface opposite to the incident surface to lose the light amount.

  In the present embodiment, the light guides 19 and 20 have been described as quadrangular columns. However, similarly to the light guide plate 21, the light exit surface may be inclined. FIG. 3 shows a planar illumination device 50 that uses light guides 25 and 26 whose exit surfaces are inclined. FIG. 3 is a diagram illustrating an example of a schematic configuration of the planar illumination device 50 according to the first embodiment of the present invention. In FIG. 3, the planar illumination device 50 is the same as the planar illumination device 10 shown in FIG. 1 except for the light guides 25 and 26. With such a configuration, the light guides 25 and 26 that convert light emitted from the light source units 15, 16, 17, and 18 into linear light sources pass through the light guides 25 and 26 and are incident surfaces. The loss of light emitted from the opposite side surface can be reduced. This further improves the light utilization efficiency.

  Further, the linear light source unit is preferably disposed on the longitudinal side surface of the light guide plate 21. By disposing the linear light source unit on the longitudinal side surface of the light guide plate 21, the distance that light propagates through the light guide plate 21 can be shortened, and the light absorption loss in the light guide plate 21 can be reduced.

  In this embodiment, the rod-shaped light guides 19 and 20 are used to convert the light emitted from the light source units 15, 16, 17, and 18 into linear light sources. An optical system that scans or diffuses light emitted from a light source in a one-dimensional direction using a one-dimensional diffusion element such as a cylindrical lens or a diffraction element is disposed on the back surface of the light guide plate 21 and is folded and guided by a prism or a mirror. It is good also as a structure which injects into the optical plate 21 (for example, refer FIG. 4).

  FIG. 4 is a diagram illustrating an example of a schematic configuration of the planar illumination device 60 according to the first embodiment of the present invention. In FIG. 4, the planar illumination device 60 arranges a polygon mirror for converting light emitted from the light source unit 61 into a linear light source on the back surface of the light guide plate 21. FIG. 4A shows a schematic configuration diagram of the planar illumination device 60 as viewed from the back. FIG. 4B shows a schematic diagram of the configuration of the side surface of the main part of the planar illumination device 60 as viewed from the direction of the arrow C in FIG.

  4 (a) and 4 (b), the light emitted from the light source unit 61 that collectively emits RGB light is branched by the half mirror 62, and one light is directly directed to the polygon mirror 64, and the other light is emitted. Light travels toward the polygon mirror 64 via the mirror 63, is deflected and scanned by different reflecting surfaces of the polygon mirror 64, converted into parallel light by the Fresnel cylindrical lenses 65a and 65b, and is converted into parallel light by the triangular prism-shaped light guides 66a and 66b. It is folded 180 degrees and enters the light guide plate 21. If the planar illumination device 60 is configured in this way, the light source parts 61 are gathered in one place, and the cost can be reduced.

(Second Embodiment)
FIG. 5 is a diagram illustrating an example of a schematic configuration of a planar illumination device 70 according to the second embodiment of the present invention. FIG. 5A shows a schematic configuration diagram of the planar illumination device 70 as viewed from above. FIG. 5B shows a schematic diagram of the configuration of the side surface of the main part of the planar illumination device 70 as viewed from the direction of the arrow D in FIG. 5A and 5B, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  5A and 5B, the light guide plate 71 receives light from an incident surface facing the light guides 19 and 20, and emits light from the main surfaces 71a, 71b, 71c, and 71d. The main surfaces 71a and 71c of the light guide plate 71 are substantially parallel, and the main surfaces 71b and 71d are configured to be inclined surfaces such that the light emission side is convex. The back surface 71e is configured to incline from the incident surface side toward the center and become thinner toward the center. Here, when the main surfaces 71a and 71c are virtually extended toward the center, they are configured to intersect with the back surface 71e.

  The back surface 71e is formed with a deflection groove for deflecting light incident on the light guide plate 71 by total reflection and directing it toward the main surfaces 71a to 71d. The deflection groove is substantially parallel to the entrance surface. It is configured.

  In the planar illumination device 70 configured as described above, the laser light emitted from the light source units 15, 16, 17, and 18 that collectively emit the RGB light is linearly emitted by the light guides 19 and 20. And is incident from both side surfaces of the light guide plate 71.

  Here, since each side surface of the light guides 19 and 20 is perpendicular to the polarization plane of the light emitted from the light source units 15, 16, 17 and 18, or parallel to the polarization, Polarized light is maintained when reflected and propagated inside the light 20, and light with uniform polarization is emitted from the light guides 19, 20 perpendicularly to the light exit surfaces 19 a, 20 a, and the main surface 71 a of the light guide plate 71 and It is incident at an angle substantially parallel to 71c.

  The propagating light 22 incident on the light guide plate 71 from the light guide 19 side travels in the light guide plate 71 substantially parallel to the main surface 71a, and almost all of the light flux is totally reflected by the deflection groove provided on the back surface 71e. The light is deflected and emitted from the main surfaces 71 a and 71 b as irradiation light 24.

  At this time, when the main surface 71a of the light guide plate 71 is extended, the light guide plate 71 is configured to intersect with the back surface 21e. Therefore, the propagation light 22 that propagates substantially parallel to the main surface 71a reaches the center of the light guide plate 71. During this period, most of the light is emitted and there is no light that escapes to the opposite side surface, so that it is possible to prevent light loss as in the conventional configuration. The same applies to the propagation light 23.

  At this time, the deflection grooves provided on the back surface 71c are parallel to the incident surface, that is, perpendicular to the propagation lights 22 and 23 inside the light guide plate 71. Light is emitted.

  The planar illumination device 70 configured as described above has an advantage that it is thin and has high light utilization efficiency and emits light with uniform polarization, as in the first embodiment. Furthermore, since the distance that light propagates through the light guide plate 71 is short, loss due to light absorption in the light guide plate 71 can be reduced.

  The absorption rate of light varies from wavelength to wavelength, and in particular, the absorption rate of blue light is large.If the display screen is enlarged, it may cause color unevenness.However, in this embodiment, loss due to absorption is small and color unevenness is also caused. Hard to occur.

  In the present embodiment, the main surfaces 71a to 71d of the light guide plate 71 are configured to have a convex shape, but the main surfaces may be configured to have an uneven shape. FIG. 6 shows a side view of a planar illumination device 80 using a light guide plate 81 whose main surfaces 81a to 81d are inclined in a W shape. The planar illumination device 80 shown in FIG. 6 is the same as the second embodiment shown in FIGS. 5A and 5B except for the light guide plate 81, and a description thereof will be omitted. The planar illumination device 80 is configured such that light from the light guides 19 and 20 enters the main surfaces 81a and 81c substantially in parallel, and has the same effect as in the second embodiment. By configuring the light guide plate 81 in this way, the planar illumination device 80 can be configured to be thinner.

  In addition, the light guide plate 81 shown in FIG. 6 may be a flat surface instead of a convex slope as long as the thickness of the central portion can ensure a sufficient strength.

  In the present embodiment, since light incident from one side surface is emitted while propagating to the center of the light guide plates 71 and 81, the light guide plates 71 and 81 are divided at the center, that is, from one side. It is good also as a V-shaped light-guide plate in which only light enters.

  In addition, the planar lighting devices 70 and 80 have side shapes similar to the side shapes of the light guide plate 71 and the light guide plate 81 shown in FIGS. 5 and 6 instead of the light guide 19 or the light guide 20. A light guide may be used. By configuring the planar illumination device in this way, it is possible to reduce the light amount loss in the light guide.

  Moreover, the liquid crystal display device as shown in FIG. 2 shown in the first embodiment can also be configured by using the planar lighting device shown in the second embodiment as a backlight lighting device. As a result, a liquid crystal display device having good color reproducibility even on a large screen, high luminance, and little luminance unevenness can be realized. A thin liquid crystal display device can also be realized.

(Third embodiment)
FIG. 7 is a schematic diagram illustrating an example of a configuration of a side surface of a main part of a planar illumination device 90a according to the third embodiment of the present invention. In FIG. 7, the planar illumination device 90 a further includes a prism sheet 27 arranged in a V shape along the inclined surfaces of the main surfaces 21 a and 21 b of the light guide plate 21 as compared with the first embodiment. The prism sheet 27 adjusts the emission angle distribution of the light emitted from the light guide plate 21 by starting up part of the light emitted from the light guide plate 21 and recycling the part of the light. At this time, if the prism sheet 27 is arranged in a planar shape, a part of light (for example, emitted light 24x) is lost, but by bending the prism sheet 27 along the light guide plate 21, Normally lost light can be returned to the light guide plate 21 again.

  FIG. 8 is a schematic diagram showing an example of the configuration of the side surface of the main part of the planar illumination device 90b according to the third embodiment of the present invention. In FIG. 8, the planar illumination device 90 b further includes a flat diffuser plate 28 or a lenticular lens along the main surfaces 21 a and 21 b of the light guide plate 21 as compared with the first embodiment. 12A and 12B, in the conventional light guide plate 107 having a mountain-shaped bottom surface, when a flat diffuser plate is disposed along the main surface 107a, the bottom surface of the light guide plate 107 is formed at the center portion. Since the distance to the diffusion plate is close, there is a problem that it is difficult to make the emitted light uniform. On the other hand, in the light guide plate 21 shown in FIG. 8, the thickness of the central portion is reduced and the bottom surface is flat. For this reason, since the distance between the bottom surface of the light guide plate 21 and the diffusion plate 28 can be increased, the emitted light 24 can be made uniform even if the light guide plate 21 is thin. The same applies to the case where a lenticular lens is disposed instead of the diffusion plate 28.

  FIG. 9 is a schematic diagram illustrating an example of a configuration of a side surface of a main part of a planar illumination device 90c according to the third embodiment of the present invention. In FIG. 9, the planar illumination device 90 c has a fine periodic structure (hereinafter referred to as a sub-wavelength grating 29) on the slope of the emission surface of the light guide plate 21, as compared with the planar illumination device 90 b shown in FIG. 8. Form. When the sub-wavelength grating 29 is formed on the slope of the light exit surface of the light guide plate 21 by a method such as nanoprinting, effects of polarization separation and wavelength separation can be obtained. Further, by forming the sub-wavelength grating 29 on the slope of the light exit surface of the light guide plate 21, the sub-wavelength grating 29 can be protected by the V-shaped slope of the light guide plate 21 and the diffusion plate 28. Also, by sealing the space between the light guide plate 21 and the diffusion plate 28, the sub-wavelength grating 29 can be effectively protected from dust and the like.

  FIG. 10 is a schematic diagram illustrating an example of a configuration of a side surface of a main part of a planar illumination device 90d according to the third embodiment of the present invention. In FIG. 10, the planar lighting device 90 d is different from the first embodiment in the shape of the light guide plate 21. The main surface of the light guide plate 21 is composed of a plurality of inclined surfaces configured such that the thickness decreases toward the center, and a plurality of incident surfaces disposed between the inclined surfaces. Further, the plurality of incident surfaces of the light guide plate 21 are configured such that substantially parallel light irradiated from both end face directions is incident thereon. Thereby, the light guide plate 21 can be reduced in weight, and the light absorption loss in the light guide plate 21 can be reduced.

  Next, the manufacturing method of the light-guide plate which concerns on the 1st-3rd embodiment of this invention is demonstrated. FIG. 11 is a diagram illustrating a method for manufacturing the light guide plate 21 according to the first embodiment of the present invention. Referring to FIG. 11, for example, the light guide plate 21 according to the first embodiment is formed by injection molding, and gates 29 a and 29 b for injecting resin are formed in the thinnest part of the side surface orthogonal to the light incident surface. Provided. The same applies to the method of manufacturing the light guide plate according to the second and third embodiments. Thereby, at the time of manufacture of a light-guide plate, resin can be made to flow easily, residual stress can be relieved, and birefringence can be reduced.

  The planar illumination device of the present invention and the liquid crystal display device using the same can be applied to a large display, a high brightness display, and the like.

The figure which shows an example of schematic structure of the planar illuminating device 10 which concerns on the 1st Embodiment of this invention. The figure which shows schematic structure of the liquid crystal display device 40 which used the planar illuminating device 10 of FIG. 1 as a backlight illuminating device. The figure which shows an example of schematic structure of the planar illuminating device 50 which concerns on the 1st Embodiment of this invention. The figure which shows an example of schematic structure of the planar illuminating device 60 which concerns on the 1st Embodiment of this invention. The figure which shows an example of schematic structure of the planar illuminating device 70 which concerns on the 2nd Embodiment of this invention. The figure which shows the side view of the planar illuminating device 80 using the light-guide plate 81 in which the main surfaces 81a-81d inclined in the W shape. The schematic diagram which shows an example of a structure of the side surface of the principal part of the planar illuminating device 90a which concerns on the 3rd Embodiment of this invention. The schematic diagram which shows an example of a structure of the side surface of the principal part of the planar illuminating device 90b which concerns on the 3rd Embodiment of this invention. The schematic diagram which shows an example of a structure of the side surface of the principal part of the planar illuminating device 90c which concerns on the 3rd Embodiment of this invention. The schematic diagram which shows an example of a structure of the side surface of the principal part of the planar illuminating device 90d which concerns on the 3rd Embodiment of this invention. The figure explaining the manufacturing method of the light-guide plate 21 which concerns on the 1st Embodiment of this invention. The figure which shows schematic structure of the conventional planar illuminating device 100.

Explanation of symbols

10, 50, 60, 70, 80, 90, 100 Surface illumination device 11 Laser light source 11R Red laser light source (R light source)
11G Green laser light source (G light source)
11B Blue laser light source (B light source)
12R Red laser light (R light)
12G color laser light (G light)
12B Blue laser light (B light)
13, 14 Dichroic mirror 15, 16, 17, 18, 61 Light source 19, 20, 25, 26, 105, 106 Light guide 19a, 20a Light exit surface 19b, 20b Side surface 21, 71, 81, 107 Light guide plate 21a, 21b, 71a, 71b, 71c, 71d, 81a, 81b, 81c, 81d, 107a Main surface 21c, 71e, 81e, 107b Back surface 22, 23 Propagated light 24 Illuminated light 27 Prism sheet 28 Diffuser plate 29 Sub-wavelength grating 30 Liquid crystal display Panel 31, 37 Polarizing plate 32, 36 Glass plate 33 Liquid crystal 34 RGB pixel 35 Color filter 40 Liquid crystal display device 62 Half mirror 63 Mirror 64 Polygon mirror 65a, 65b Fresnel cylindrical lens 66a, 66b Triangular prism light guides 101, 102, 103,104 The light source

Claims (16)

A linear light source unit for emitting linear laser light;
A light guide plate that makes the linear laser light incident from opposite end faces and emits from one main surface;
The main surface of the light guide plate is composed of four inclined surfaces arranged in series between the end surfaces on both sides ,
The light guide plate is configured such that the thickness decreases toward the center , and two central inclined surfaces of the four inclined surfaces have a convex V-shape. A planar lighting device. A linear light source unit for emitting linear laser light;
A light guide plate that makes the linear laser light incident from opposite end faces and emits from one main surface;
The main surface of the light guide plate is composed of a plurality of inclined surfaces configured to be thinner toward the center, and a plurality of incident surfaces disposed between the inclined surfaces and the inclined surfaces,
The planar illumination device according to claim 1, wherein the plurality of incident surfaces of the light guide plate are configured so that substantially parallel light irradiated from the end surface directions on both sides is incident. 3. The planar illumination device according to claim 1, wherein a thickness of a central portion of the light guide plate is thinner than thicknesses of end faces on both sides of the light guide plate. The light guide plate has a deflector that deflects light incident on the light guide plate toward the main surface on the back surface facing the main surface,
At least one of the plurality of inclined surfaces, when extended the inclined surface virtually, characterized in that it is configured to intersect a portion of said back surface, the surface illumination according to claim 1 or 2 apparatus. Further comprising a prism sheet for adjusting the emission angle distribution of the light emitted from the light guide plate,
The prism sheet is characterized in that it is disposed along the inclined surface of the light guide plate, a planar lighting device according to claim 1 or 2. Diffusing plate on the main surface of the light guide plate, or wherein placing the lenticular lens, the planar lighting device according to claim 1 or 2. The planar illumination device according to claim 6 , wherein a fine periodic structure is formed on the inclined surface of the light guide plate. The light guide plate, characterized in that it comprises a small diffusing particles therein, the planar lighting device according to claim 1 or 2. The linear light source unit is configured to emit light substantially parallel to the main surface of the light guide plate toward both end faces of the light guide plate,
The light guide plate is provided with a plurality of deflection grooves for deflecting substantially parallel light incident from the linear light source unit by total reflection on a back surface facing the main surface. The planar illumination device according to 1 or 2 . The linear light source unit is
A laser light source that emits diverging light; and
A collimating element that converts divergent light emitted from the laser light source into substantially parallel light;
The planar illumination device according to claim 9 , further comprising: a rod-shaped light guide that allows light emitted from the collimator element to be incident from an end surface and to be emitted from a side surface. The linear light source unit is
A laser light source that emits diverging light; and
A collimating element that converts divergent light emitted from the laser light source into substantially parallel light;
The planar illumination device according to claim 9 , further comprising a polygon mirror that deflects and scans the light emitted from the collimating element. The linear light source unit is
A laser light source that emits diverging light; and
A collimating element that converts divergent light emitted from the laser light source into substantially parallel light;
The planar illumination device according to claim 9 , further comprising: a one-dimensional diffusion element that diffuses light emitted from the collimating element in a one-dimensional direction by refraction, diffraction, or scattering. 10. The surface according to claim 9 , wherein the light guide plate is configured such that the deflection groove is a curved surface, and a tangent to the curved surface is 30 ° to 60 ° with respect to the main surface. Illuminator. 3. The planar illumination device according to claim 1, wherein the light guide plate is formed by injection molding, and a gate is provided at a thinnest portion of a side surface orthogonal to a light incident surface. The linear light source unit is characterized by being located in a longitudinal side surface of the light guide plate, a planar lighting device according to claim 1 or 2. A laser light source for emitting laser light;
A rod-shaped light guide that makes the laser light incident from both end faces facing each other and emits from the side surfaces;
A light guide plate that makes light emitted from the light guide incident from an end surface and emits light from one main surface;
The light guide is formed such that a cross section parallel to the end surfaces on both sides is rectangular,
The side surface from which the light of the light guide is emitted is composed of four inclined surfaces arranged in series between the end surfaces on both sides ,
The light guide is configured such that the thickness decreases toward the center , and two central inclined surfaces of the four inclined surfaces have a convex V-shape. A planar lighting device.

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